Most recent version of Buildcraft for 1.11.2, Mekanism Generators, Mekanism, and Forge.

Reproduce crash by simply installing these mods and trying to run Minecraft.

I can provide the full log if needed, but you shouldn't need it, just update fluid handler API for your code.

https://pastebin.com/X3PLAHnq

Nevermind, had to double check and noticed that this issue was already open. Sorry (didn't see it the first time around.)